Coupling for high frequency circuits



June 12, 1934.

E. ZEPLER COUPLING FOR HIGH FREQUENCY CIRCUITS Filed Sept. 20, 1930 I El INVENTOR ERICH ZEPLER BY k /&rr2/-(4;L

ATTORNEY instance.

diate neighborhood of the receiving room, as is a very high capacity to ground, such an arrange- 4 tion of capacity attenuation of lead-in conduc- Patentecl June 12, 1934 COUPLING FOR HIGH FREQUENCY CIRCUITS Erich Zepler, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. 11., Berlin, Germany, a corporation of Germany Application September 20, 1930, Serial No. 483,247 In Germany October 5, 1929 6 Claims.

ferred through a transformer 4 between high frequency apparatus and an antenna.

In what follows a circuit scheme is disclosed whereby it is feasible to preclude any harmful attenuation or reduction in volume due to the cable.

According to the invention, an inductance is inserted between the cable line and the ground, the same being so proportioned that it will tune the cable circuit exactly or roughly to the incom- 5 ing wave. In this manner volumes are obtained of the same order of magnitude as in the case of direct antenna reception.

So far as the operation of this scheme is concerned, it is immaterial at what particular point 7 along the cable the inductance is added, though for practical reasons it will mostly have to be disposed at a point Where the cable is connected with the receiver.

The cable circuit tuning inductance 6 may be connected either directly with the grid of the input tube (Figure 3); or else a more favorable receiving volume may be assured by the interposition of a second tuning circuit 8 (Figure 4) and suitably chosen coupling (transformer prin- 30 ciple), as shown in Figures 4 and 5 either inductive as shown in Figure 4 or inductive and capacitive as shown in Figure 5. For tuning the cable circuit, either a fixed or a variable inductance will have to be employed according to 5 whether one fixed wave length or different waves are to be received. If a variable inductance is employed, the same may be either a variometer or else it may be varied in steps. Owing to the fact that the damping of cables is mostly considerable, wave steps of 5% will mostly be sufficient. In an arrangement of this kind, a unicontrol change-over switch or link mechanism 10 adapted to change the tuning of the cable or antenna coupling circuit automatically together 5 with the tuning of the receiver is most convenient.

If several receivers are to be connected with the same antenna, then a scheme as illustrated in Figure 5 may be employed. The same requires as many cables as there are receivers. The ca- It happens quite often in the reception of radio waves that the place or point where the receiver must be mounted, is unserviceable for the mounting of an antenna, the reasons underlying the 5 adoption of such a scheme residing, for example,

in strong local disturbances or in that the receiving place is markedly screened from incoming waves by high buildings in the vicinity, while affording little protection from atmospherics, for

In cases like that, various ways and means are known to alleviate the trouble; for example, the antenna and the receiver may be installed at some distance from the receiving rooms the receiver may be designed for remote control, while the audio frequency or modulation energy delivered by the last stage is transmitted to a translating or relaying device.

If the disturbances are confined to the immeoften true in the case of trouble due to machines, neighboring sending antennae, etc., then it is frequently suflicient to mount the receiving antenna at a distance of, say, meters from the 25 receiving room. In order to preclude all chances of disturbances the connection between antenna and receiver should consist, mainly, of a cable having a grounded metallic sheath. Inasmuch as the feed line contained inside the cable presents ment ordinarily is attended with a considerable attenuation in volume owing to the harmful capacitive shunt thus created.

In the accompanying drawing, in connection 35 with which my invention is more fully described, Figures 1 and 2 illustrate antenna lead-in structures, attenuating transferred energy, and Figures 3 to 6 inclusive are illustrative of the present invention directed towards the eliminators.

In the scheme shown in Figure 1 which represents the normal case of capacitive coupling from a high frequency circuit usually the antenna to 45' high frequency apparatus through a condenser 2, 100

the attenuation is given by the ratio Antenna capacity Antenna capacity+cable capacity 55 coupling (Figure 2), wherein energy is transpacity provided in this case between antenna and, cable should then be chosen so that inter-action between the various receivers will be diminished to a reasonable amount. An arrangement of this sort is illustrated in Figure 6 wherein several receivers are shown individually connected by cables K to a single antenna A.

Having thus described my invention, what I claim is:

1. In combination, a high frequency cirucit, a

tunable circuit, a cable transmission line for coupling the circuits together, a variable inductor coupled between the line and ground for eliminating the efiects of the distributed capacity thereof and unicontrol means for varying the tuning of the tunable circuit and the inductance of the inductor.

2. In combination, an antenna, a tunable circuit, a shielded transmission line for coupling the circuits together, a variable inductor coupled between the line and ground for eliminating the effects of the distributed capacity thereof and unicontrol means for varying the tuning of the tunable circuit and the inductance of the inductor.

3. In a signal receiving system, a receiver comprising an electron discharge device having a control electrode, an antenna, a linear feed line extending between and directly connected to said antenna and the control electrode of said electron discharge device, a shield for said line, and a supplemental tunable inductance one side of which is directly connected to said line and the other side of which is at substantially the same potential as said shield for eliminating the effects of the distributed capacity thereof.

4. A radio receiving system having, in combination, an antenna, a receiver possessing at least one tuned circuit, a line extending between said antenna and said receiver, a shield around said line and connected to ground, a tunable inductance connected between said line and ground for compensating for the distributed capacity between said line and said grounded shield, and uni-control means for simultaneously varying said inductance and said tuned circuit of said receiver.

5. A radio receiving system comprising a single antenna, a plurality of remote receivers, lines individually connecting each receiver with said antenna, shields around said lines, and individual tunable inductors connected to each of said lines and to ground for eliminating the ei fects of the distributed capacity of said lines, and uni-control means at each receiver for simultaneously varying the tuning inductor and its associated receiver.

6. A radio receiving system having, in combination, an antenna, a receiver possessing at least one tuned circuit, a line extending between said antenna and said receiver, a shield around said line, a tunable inductance directly connected to said line and elfectively connected to said shield for compensating for the distributed capacity between said line and shield.

ERICII ZEPLER. 

